Primary cell



United States Patent PRMARY CELL also contain zirconium in amount between 0.001 per cent and 0.1 per cent, the higher amounts of Zirconium are usable with the alloys containing little or no aluminum While the lower amounts of zirconium are usable in the 5 alloys containing the higher amounts of aluminum. If Ashford B. Fry, Percy F. George, and Roy C. Kirk, Middesired, beryllium in amount between 0.0005 and 0.005

land, Mich assignors to The Dow Chemical Company, may also be included with advantage. Preferred propor- Midland, Mich a corporation of Delaware tions of the alloying elements are: 0.75 to 1.2 per cent 4 r D of aluminum, 0.25 to 0.5 per cent of zinc, 0.1 to 0.3 er N0 Dmmng' ggi fig gg gg 1952 cent of calcium, 0.001 to 0.003 per cent of beryllifrn,

and 0.01 to 0.05 per cent of Zll'COIllllD'l, the balance being 4 Claims- L 1351l39) commercial magnesium containing not more than 0.002 per cent of iron, 0.001 per cent of nickel, and 0.05 per cent of manganese. A generally desirable anode alloy com- The invention relates to an improved primary cell position is: l per cent of aluminum, 0.4 per cent of zinc, utilizing magnesium as the anode material, a cathode of 0.15 per cent of calcium, and 0.001 per cent of beryllium carbon depolarized with manganese dioxide, and an elecwith or Without 0.05 per cent of zirconium, the balance trolyte comprising a water-soluble bromide of an alkali being commercial magnesium containing not more than metal, alkaline earth metal or ammonium. 0.002 per cent of iron, not more than 0.001 per cent of A number of disadvantakes inure to primary cells of nickel, and not more than 0.05 per cent of manganese. the foregoing makeup which limit their usefulness particu- In making up cells in accordance with the invention, the larly when in the form of non-spillable or dry cells in anode is generally made in the form of a cup or the like which the anode is the container for the electrolyte and usually cylindrical in shape so as to form the container for cathode. the other principal elements of the cell, viz. the cathode One of these disadvantages, which is referred to herein mix and the electrolyte, as in conventional dry cell conas delayed action, is that the cells do not always attain full struction employing magnesium in the anode alloy, e. g. working voltage on attempting to reuse them following see U. S. Patent 2,547,907. The anode material is prea rest period after a use. The delay may be as much as pared by melting a suitable quantity of magnesium of the 100 seconds or more depending upon the amount of use requisite purity preferably in a graphite or alloy steel and intervening rest as Well as the age of the cell. An- 7 crucible so as to avoid excessively contaminating the other disadvantage is that the anode whether flat or in cup magnesium with other metallic elements especially iron, form as the container of the cell oftentimes cracks or copper, and nickel. The metallic elements to be alloyed leaks before the cell is exhausted. with the magnesium are introduced in this order: zir- It is the principal object of the invention to provide an coniurn (if any), zinc, aluminum, beryllium (if any), improved primary cell having a high capacity employing 5 and lastly calcium. magnesium in the anode, a manganese dioxide depolarized After melting together the metallic elements of the cathode, and an aqueous electrolyte comprising an alkali alloy, it is cast into billet form, scalped to remove the metal, alkaline earth metal or ammonium bromide in casting skin, and then die-expressed (extruded) into rod which the foregoing disadvantages are eliminated, if not of a suitable diameter for impact extrusion into cell cans substantially overcome. Other objects and advantages of (anodes). For example, the molten alloy may be cast the invention Will appear as the description proceeds. into billets about 4 inches in diameter and 1 foot long, The foregoing and related objects are attained in and, after scalping, the billet is extruded into rod 1% accordance with the invention by forming the anode of the inches in diameter. Slugs for impact extrusion are made cell of an especially formulated magnesiurn-base alloy by cutting the extruded rod into pieces of suitable length. as herein set forth. In brief, the anode material of the Slugs inch long are suitable for making cans for F-size cell comprises a magnesium-base alloy containing from dry cells (nominal diameter 1% inches, nominal height 0.1 to 0.7 per cent of zinc, from 0.05 to 0.5 per cent of 3%; inches); D-size cans, which have the same diameter calcium, the balance being commercial magnesium conbut a height of 2% inches, require slightly thinner slugs. taining not over 0.005 per cent of iron, not over 0.002 A suitable thickness for the wall of the can is 0.05 inch per cent of nickel, and not over 0.1 per cent of manganese. but other thicknesses may be used. The alloy, we have found, may also include up to about Examples of dry cells embodying the invention are 1.5 per cent of aluminum, the aluminum having the effect tabulated in the following table which also sets forth of giving the cell a higher capacity. The anode alloy may performance data of the cells.

Table Anode Composition 3 in Percent Delayed Action in Seconds Capacity Cracking Cells Group General Purpose 3 R. R. Lantern 4 General R R- No. Purpose, Lafitem General B. R.

Al Zn Mn Ga Zr Be Mmutes Hours 6 Purpose, Lantern,

Min. Max. Av. Min. Max. Av 1.2 Volt Mmutes Ems 1 3 cells of each anode composition.

2 Balance commercial Mg, containing not over 0.005% Fe, 0.002% Ni, 0.1% M11 the inside diameter of the lined cans.

In making up the cells shown in the table, the electrolyte used consisted of an aqueous solution containing 250 grams per liter of magnesium bromide (MgBrz) and 0.2 gram per liter of sodium chromate (NHZCIO). The cathode mix was composed of 91 parts of African manganese dioxide, 3 parts of barium chromate (BaCrOi) and 6 parts of acetylene black per 100 parts of the mix which was moistened with the foregoing electrolyte solution in the proportion of 300 cc. of electrolyte solution per 1000 grams of the dry Each anode, or battery can having a wall thickness of 0.05 inch, was lined with paper previously moistened with gelled or thickened electrolyte made by cooking a starch-flour mixture (75 per cent starch, per cent wheat flour) in electrolyte solution in the proportions of 1 gram of the starch-flour mixture per cc. of the electrolyte solution until the mixture thickened. The moistened cathode mix was die-expressed into cylindrical form with a diameter slightly smaller than The extruded cathode mix was cut into pieces about /2 inch shorter than the depth of the cans and a piece inserted into each can. The weight of the cathode mix for the D-size cans was grams, for the F-size cans 102 grams. A graphite rod inch in diameter and longer than the can was then forced into the center of the cathode mix in each can to -T.

form the electrode for the cathode mix. The forcing of the electrode into the cathode mix caused it to become tightly packed against the lining of the can. A cardboard washer was then inserted over the protruding end or the electrode and the remaining space in the top of the can above the washer was filled with molten sealing wax which formed'a seal for the top of the cell between the central electrode and the inside of the top of the can.

As indicated in the table cells of two sizes, formulated as described, were submitted to three types of tests, viz.: delayed action, capacity, and cracking tests. The delayed action readings and cracking observations were made incidental to the capacity tests which are modifications of standard tests referred to in the Circular of National Bureau of Standards C466, issued December 1, 1947, as the general purpose 4-ohm intermittent test (page 10), which was applied to D-size cells, and the Railroad Lantern battery test (page 11), which was applied to F-size cells only.

In the general purpose test inDsize cells (cell group Nos. 1 and 7) each of 3 cells was discharged through a resistance of 4 ohms for 5 minutes each day until the voltage of each cell (after delayed action) declined to 1.0 volt. The average of the total number of minutes of discharge of each cell is entered in the table under Capacity in the column headed General purpose, minutes to 0 volt. The seconds of time required for each D-size cell to attain 1 volt at the beginning of each of the 5 minute discharge period was recorded, and, in the table in the column headed General purpose under delayed action, there was entered the minimum, maximum, and

average of all such times. Also, during this general purpose test, the total number of minutes of discharge of each D-size cell before the cell can cracked, was noted, and the aver-age of such total number of minutes for each of the 3 cells in the group was recorded in the table under crack ing in the column headed General purpose, minutes.

In the tests applied to F-size cells, the railroad lantern battery test of the aforesaid circular was modified to the extent that the resistance use in the discharge was 10.7

instead of 8 ohms per cell and the test was concluded when the voltage of each cell in'the group declined to 1.2 instead of 0.9 as in the circular. in the'railroad lantern battery test each of a group of 3 cells was discharged through the resistances for the first "/2 hour ofevery consecutive hour for 8 hours each day (total of 4 hours of discharge per day) until the voltage of each cell declined to 1.2 volts. The average or the total number of hours of such discharging was entered in the table as capacity under the column headed R. R. lantern, hours to 1.2 volt for groups numbered 2 to 6, inclusive, 8, 9, and 10. The delayed action of these cells was observed at the beginning of the first and last of the /2 hour discharges each day. Of the delayed action times so observed, there was recorded in the table under delayed action in seconds in the column headed R. R. lantern, the minimum and maximum seconds as well as the average of all the observed delays. During this test, the average of the hours of discharge until cracking of the cans was observed was recorded in the table for each cell group in the last column.

it is manifest from the examples of cells formulated in accordance with the invention, i. e. cells in groups Nos. 1 to 10, inclusive, that the average delay in attaining a working voltage in the case of the D-size cell was not over 0.04 second on the average and no D-size cell had a delay greater than 2.3 seconds. At the same time, the D-size cells showed a capacity of 378 to 525 minutes. The length of time the D-size cells resisted cracking was as much as 390 minutes. F-size cells, although submitted to a more drastic discharge schedule in the railroad lantern test which produces a much greater delayed action than the 4-ohm general purpose test, showed low delayed action with high capacity and good resistance to cracking.

The electrolyte concentration does not appear to be sharply critical and may range from about to 500 grams of the bromide salt per liter of solution, generally desirable concentrations being from about 200 to 300 grams per liter. A corrosion inhibiting amount of a chromic acid salt such as an alkali metal, alkaline earth metal (including magnesium), or ammonium salt of chromic acid may be included in the electrolyte, as already indicated in the examples, in a concentration of 0.01 to 5 grams per liter.

Although in the examples the cathode mix is shown containing a small amount of an insoluble chromate, e. g. barium chromate, it is to be understood that other insoluble chromates may be used or omitted entirely, if desired.

it is to be understood that the foregoing description is illustrative rather than strictly limitative, and that the other embodiments of the invention are possible within the spirit of the invention and the scope of the following claims.

We claim:

1. In a primary cell the combination of an anode comprising a magensium-base alloy containing up to 1.5 per cent of aluminum, from 0.1 to 0.7 per cent of zinc, from 0.05 to 0.5 per cent of calcium, the balance being commercial magnesium containing not'over 0.005 per cent of iron, not over 0.002 per cent of nickel, and not over 0.1 per cent of manganese, a magnanese dioxide depolarized cathode, and an electrolyte comprising an aqueous solution of an inorganic bromide selected from the group consisting of the water-soluble bromides of the alkali metals, alkaline earth metals, and ammonium.

2. In a primary cell the combination of an anode comprising a magnesium-base alloy containing up to 1.5 per cent of aluminum, from 0.l to 0.7 per cent of zinc, from 0.05 to 0.5 per cent'of calcium, from 0.0005 to 0.005 per cent beryllium, the balance being commercial magnesium containing not over 0.005 per cent of iron, not over 0.002 per cent of nickel, and not over 0.1 per cent of manganese, a manganese dioxide depolarized cathode, and an electrolyte comprising an aqueous solution of an inorganic bromide selected from the group consisting of the water-soluble bromides of the alkali metals, alkaline earth metals, and ammonium.

3. In a primary cell the combination of an anode comprising a ma nesium-base alloy containing from 0.75 to 1.2 per cent of aluminum, from 0.25 to 0.5 per cent of zinc, from 0.1 to 0.3 per cent of calcium, from 0.001 to 0.003 per cent of beryllium, from 0.01 to 0.05 percent of zirconium, the balance being commercial magnesium containin not over-0.005 per cent of iron, not over 0.002 per cent of nickel, and not over 0.1 per cent of manganese,

a manganese dioxide depolarized cathode, and an electrolyte comprising an aqueous solution of an inorganic bromide selected from the group consisting of the watersoluble bromides of the alkali metals, alkaline earth metals and ammonium.

4. In a primary cell having in combination a manganese dioxide depolarized cathode, an aqueous electrolyte comprising a water-soluble bromide of an alkali, alkaline earth metal or ammonium, the improvement which consists in forming the anode of commercial magnesium alloyed With from 0.1 to 0.7 per cent of Zinc, from 0.05 to 0.5 per cent of calcium, said commercial magnesium containing not over 0.1 per cent of manganese, not over 0.005 per cent of iron and not over 0.002 per cent of nickel.

References Cited in the file of this patent UNITED STATES PATENTS Bonner Feb. 24, Brown et al. Aug. 20, Wood Jan. 2, Stroup et al. July 10, De Long et al. Sept. 6, Louzos Dec. 26, Blake Sept. 30, Reid Nov. 4,

FOREIGN PATENTS Great Britain Mar. 21, France Apr. 5,

Great Britain Aug. 16, 

1. IN A PRIMARY CELL THE COMBINATION OF AN ANODE COMPRISING A MAGENSIUM-BASE ALLOY CONTAINING UP TO 1.5 PER CENT OF ALUMINUM, FROM 0.1 TO 0.7 PER CENT OF ZINC, FROM 0.05 TO 0.5 PER CENT OF CALCIUM, THE BALANCE BEING COMMERCIAL MAGNESIUM CONTAINING NOT OVER 0.005 PER CENT OF IRON, NOT OVER 0.002 PER CENT OF NICKEL, AND NOT OVER 0.1 PER CENT OF MANGANESE, A MAGNANESE DIOXIDE DEPOLARIZED CATHODE, AND AN ELECTROLYTE COMPRISING AN AQUEOUS SOLUTION OF AN INORGANIC BROMIDE SELECTED FROM THE GROUP CONSISTING OF THE WATER-SOLUBLE BROMIDES OF THE ALKALI METALS, ALKALINE EARTH METALS, AND AMMONIUM. 